This invention relates to catheters, and more particularly, to a catheter carrying a thermistor which has a fast response to temperature changes.
It is often necessary or desirable to measure the temperature of a fluid, such as blood, within a living body and to measure changes in temperature rapidly as they occur. One example of a medical procedure which requires a catheter having a fast response thermistor is the calculation of ejection fraction. In calculating ejection fraction, it is necessary to measure changes in blood temperature as they occur. This means that it is necessary that the thermistor measure blood temperature directly rather than the temperature of the catheter on which it is mounted. In the calculation of ejection fraction, the thermistor should follow the beat-to-beat blood temperature changes so that discrete steps in the temperature curve can be observed.
Webler U.S. Pat. No. 4,796,640 discloses a catheter with a fast response thermistor suitable for use in the calculation of ejection fraction. In the specific embodiment of this patent, the thermistor is oriented with its long axis extending radially, and the conductor leading to the thermistor is bent to provide a radially extending portion that electrically couples the conductor to the thermistor. The bent portion of the conductor controls the height of the thermistor in the catheter and the bend occurs generally in the region where external conductors are bonded to the lead wires of the thermistor.